1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, and more specifically, to an LCD device having dynamically switching driving modes to reduce power consumption.
2. Description of Prior Art
With a rapid development of monitor types, novel and colorful monitors with high resolution, e.g., liquid crystal displays (LCDs), are indispensable components used in various electronic products such as monitors for notebook computers, personal digital assistants (PDAs), digital cameras, and projectors. The demand for the novelty and colorful monitors has increased tremendously.
Referring to FIG. 1 showing a schematic diagram of a liquid crystal display device according to a prior art. Liquid crystal display device 10 contains a timing controller 14, a source driver 16, a gate driver 18, and a liquid crystal panel 20 having a plurality of pixel units 22. Upon receiving clock signal from the timing controller 14, the gate drivers 18 generate scan signal to the liquid crystal panel via scan lines. Meanwhile, the source drivers 16 delivers digital image data to the liquid crystal panel 20 via data lines in response to the clock signal from the timing controller 14. As a result, the pixel units 22 show an image based on the digital image data signal and common voltage in response to the scan signal.
With reference to FIG. 2 illustrating an equivalent circuit diagram of pixel unit and source driver as shown in FIG. 1, each pixel unit 22 may simplify as a combination of resistor R and a capacitor (referred to as a liquid crystal capacitor) C. The source driver 16 will supply a bias current to charge the capacitor C to a desired voltage level based on digital image data, so that an alignment of liquid crystal molecules within the capacitor C to display various gray levels. Actually, driving ability of the source driver, dependent on output resistance of output stage and magnitude of the bias current, should be adjusted according to manifold size liquid crystal displays or data line loadings. Nevertheless, conventionally, once the source driver assembles in the LCD device, its output bias current is constant and unchangeable.
Concerning environmental conservation, in recent years, some conventional source drivers utilize charge sharing/charge recycling techniques to save output current and reduce power consumption. But such techniques spend more time on transmission from the source driver to a data line, disadvantageous to those liquid crystal displays in need of higher resolutions and shorter charging time because of insufficient charge within the data lines or capacitors.
Conventionally, the LCD device will slow frame rate in a power-saving mode to reduce power consumption. For example, the LCD device operates in a frame rate of 60 Hz in normal mode, whereas operates in another frame rate of 30 Hz in power-saving mode. Unfortunately, in spite of lower frame rate, the bias current outputted from the source driver remains constant, so actual power consumption is not expectedly reduced as much as in proportion to frame rate. As such, keeping on the constant bias current and the driving ability in the power-saving mode is inessential, supplying an adequate bias current and/or enabling charge recycling for the source driver in low frame rate is a proper proposal to efficiently save power.